Slide-valve structure



1970 A. BENDER 3,525,500

SLIDEVALVE STRUCTURE Filed Feb. 12, 1968 5 Sheets-Sheet l V PRIOR ART i 1g i Fig.1

R 17 7 PF 44 r as 3 1:? X

, 22 23 4 Alfred Bender INVENTOR.

Attorney A. BENDER SLIDE-VALVE STRUCTURE Aug. 25, 1970 .5 Sheets-Sheet 2:

Filed Feb. 12, 1968 Alfred Bender INVENTOR.

United States Patent 3,525,500 SLIDE-VALVE STRUCTURE Alfred Bender, Hofheim, Taunus, Germany, assignor to Alfred Teves G.m.b.H., Frankfurt am Main, Germany, a corporation of Germany Filed Feb. 12, 1968, Ser. No. 704,638 Claims priority, application Ggrmany, Feb. 14, 1969,

Int. Cl. F16k1/00, 11/07 US. Cl. 251324 6 Claims ABSTRACT OF THE DISCLOSURE The present invention relates to a hydraulic control and actuating device and, more particularly, to a flowdistributing slide valve adapted to be returned by elastic restoring means to its null or neutral position when the pressure of the hydraulic fluid falls to a predetermined minimum value or some other external actuating force is removed.

A piston of this type is commonly actuated by mechanical, electromagnetic, or hydraulic means which must overcome the restoring force of oppositely eflective resilient means to cause fluid outlets to be patrially opened or closed. This operation, by virtue of the shape of the valve surfaces, often brings additional pressure to bear against the piston or plunger; upon release of the external force the springs expand and return the piston to its neutral or null position.

In prior art devices, a number of attempts have been made to overcome the drawbacks inherent in this or similar valves; see H. Kiefer, US. Pat. 3,270,763 of Sept. 6, 1966 as an example. Most of the suggested improve ments introduce additional elements to augment the restoring force and counteract the fluid-force component which acts counter to the restoring force. These auxiliary means are frequently cumbersome and expensive; moreover, they are apt to contribute to the failure potential of the system through their complexity.

It is an object of my present invention toeliminate these drawbacks and to provide a reliable, simple and economical distributing slide-valve construction.

Another object is to obviate the need for external elements to support the restoring force for the valve member.

Still another object is to make the restoring force in the valve body more sensitive to minor variations in the fluid pressure.

These objects and others which will become apparent hereinafter are attained, in accordance with the present invention, through the diversion of the direction of fluid flow through the system. My invention provides at least one of the channels of the valve member connecting the supply fluid-inlet and the fluid-outlet port or compartment with cam'bered extensions to deflect the fluid flow in such a way that the resulting effective component of the momentum is directed parallel to the direction of the restoring forces and thereby enhances its effectiveness.

The above and other objects, features and advantages of my invention will become more readily apparent from ice the following description, reference being made to the accompanying drawing in which:

FIG. 1 is an axial cross-sectional view of a conventional distributing slide valve according to the prior art;

FIG. 2 is a schematic axial cross-sectional view of part of a distributing slide valve in accordance with my invention;

FIG. 2A is an enlarged cross-sectional view of a portion of the valve shown in FIG. 2 and provided with a force diagram illustrating the principles of the invention;

FIG. 2B represents a modification;

FIG. 2C is a longitudinal crosss-ectional view taken along the line IICIIC of FIG. 2B;

FIG. 3 is an axial cross-sectional view of an alternate embodiment of my invention; and

FIG. 4 is an axial cross-sectional view of yet another embodiment of my invention.

In the drawing there is shown in FIG. 2B the distributing slide valve piston or plunger axially slidable in the cylindrical valve body 114. Its central axis is, as in FIG. 2, designated at 20. The supply ports or inlet compartments 111 and 111' communicate with the outet ports or compartments 112, 112' by means of the channels 113, 113' which have a generally trapezoidal cross section. The supply and outlet ports are of identical shape and symmetrically positioned inside the valve body 114. Actuating means 33, advantageously represented by a reversible electromagnet though they could also be provided by other force elements apply the actuating force (represented at B in FIG. 2) to the plunger 16 or 115. The restoring. forces result from captive springs 16 which are prestressed, and which are supported in the spring housing 24 on angle stops 25 (see FIG. 2). The angle stops 25 are braced against the valve body 14, 114 as well as against the piston of plunger 15, 115. This arrangement permits pretensioning of the springs and makes them operative, upon displacement of the plunger, in either direction.

Fluid from the reservoir 28 is delivered at high pressure to a supply line 27' by means of a continuously operating pump 27. Line 27' terminates at the inlets (e.g. 126, 126) of the supply ports 11; 111, 111. The fluid circulates through the channels 13; 113, 113' and returns through the outlet passage (eg, 129, 129) of the outlet ports 12; 112, 112' to the line 30 which leads to the reservoir. Upon displacement of the plunger to its offnormal positions, in either direction, channels 113, 113' communicate with a compartment connected to a reversible load 31, e.g. a hydraulic motor.

As is illustrated in the embodiment of FIG. 2, the operating or actuating means push the piston in the direction of the arrow B, whereas the direction of the restoring force is indicated by the arrow PF. In prior art arrangements, shown in FIG. 1, the fluid flow from the supply port 11, through the passageway 13 and back to the outlet port 12, and roughly in the direction of the curved arrow C, can be resolved in a force diagram in which a radial component P acts normal to the piston axis 20, and an axial component P acts parallel to this axis. This axial component P is due to the Bernoulli effect, as described in US. Pat. No. 3,123,335 issued on Mar. 3, 1964 to M. C. Darling. The radial component P distributed over the entire circumference of the piston 15, is cancelled by equal and opposite forces acting upon the opposite side. However, the axial force component P is in opposition to the restoring force PF and increases the total resistance which the latter must overcome in order to return the piston to its normal or null condition. Since the spring force depends upon the coeflicient of elasticity as well as upon the degree of stress imparted upon each of the spring elements, the construction ac- 3 cording to prior art requires a greater degree of pretensioning of the springs than would be necessary if the opposing force of the fluid flow could be removed.

In FIG. 2, which shows a preferred embodiment of my invention (see also FIG. 2A) there are provided hemispherical extensions 18 of the flanks of the passageway 13 which overhang the base or floor and give the passageway essentially the shape of a hollow ellipsoid whose major axis is parallel to the base.

This interior contour, i.e. inward concavity and curvature, of the channel 13, 113 etc. affects the direction of the fluid flow which, on following the line 17 in FIG. 2 is turned around inside the hollow frustoconical shape of the extension or overhang 18 and produces a resultant momentum or force in the direction P (see FIG. 2A) whose axial component P now is oriented in a direction opposite to that of prior art component shown in FIG. 1. Thus, the effective force component of the fluid flow parallels the direction in which the restoring force PF is acting and adds to the restoring force instead of subtracting from it. With less resistance to overcome, the springs need not be pretensioned to the degree required in prior art; a decrease in the tension of the springs, and therefore, in their stiffness, results in better response to minor variations of the fluid pressure and hence contributes to the increased sensitivity of the valve and its control functions.

In another embodiment of my invention, shown in FIG. 3, the straight flanks of the passageway have, at an angle {3 of approximately to 40 to the axis 20, frustoconical extensions 19 which are connected through bores 21 with the supply and the outlet port 11 and 12 respectively at the surface of the valve member. In this manner the bores or extensions 19 are inclined to the axis 20 of the plunger and lie along on the frustoconical surface of an imaginary frustum coaxial with the axis 20. The longitudinal axes of the bores 21. are at an angle of approximately 20 to relative to the longitudinal axes of the frustoconical extensions 19, in order to direct the fluid flow generally along the arrow 17 to produce a momentum whose axial component P supports the restoring force.

In yet another embodiment of my invention, according to FIG. 4, the concave portions 18 of the flanks of the channel 13 are extended outwardly until their combined bases are twice as long as the base of the channel 13 of which they form a part. Bores 23 spaced apart in the overhangs communicate between the channel and with the supply port 11 and with the supply port 11 and the outlet port 12 respectively. Bores 23 open at the surface of the plunger 15 and include angles a of approximately 20 to 80 with the base of the passageway. As in the above disclosed construction, the direction of the fluid flow 17 is turned around, so that the operative force component here also adds to the restoring force represented by the springs. In all cases the flanks of the channels are symmetrical with respect to the median radial planes RP.

It is possible, through the methods of my invention, to reduce the pretensioning of the springs 'by 75%. For example, whereas according to prior art a restoring force of approximately 50 kp. is required to resist displacement of the piston from its neutral position, the construction according to the method disclosed above demands a resisting force of only 12 kp.

I claim:

1. In a slide valve for the control of a flowing fluid having a valve body and a valve member shiftable relatively to said body against a restoring force, the improvement wherein said valve body is formed with a fluid-inlet compartment and a fluid-outlet compartment open in the direction of said valve member, and said valve member is provided with a channel interconnecting said compartments in a neutral position of the Valve member, said channel having a configuration at least in the direction of flow of the fluid from said inlet compartment to said outlet compartment applying a component of force to said member in aiding relationship to said restoring force and tending to return said member to said neutral position upon its displacement therefrom, said body being generally cylindrical and said compartments are inwardly open annular grooves, said valve member forcing a plunger axially shiftable in said body, said channel being an outwardly open circumferential groove formed in said plunger and having a pair of axially spaced flanks and a base defining same, said flanks at least partly overhanging said base, said flanks being at least in part formed by bores inclined to the axis of said plunger and extending outwardly from the channel, said valve member further having other bores formed in said plunger communicating with the first-mentioned bores and open at a surface of said member juxtaposed with said body adjacent the mouth of said outwardly open circumferential groove.

2. The improvement defined in claim 1, further comprising prestressed resilient means bearing upon said body and said member for applying said restoring force to the latter.

3. The improvement defined in claim 1 wherein said flanks are concave inwardly into said channel.

4. The improvement defined in claim 1 wherein said flanks are disposed symmetrically on opposite sides of a radial median plane through said channel.

5. The improvement defined in claim 1 wherein said channel is of generally trapezoidal section with the broad side of the trapezoid lying along said base.

6. A slide valve for the control of a flowing fluid comprising a generally cylindrical valve body and a valve member forming a plunger axially shifta-ble in said body against a restoring force, said valve body being formed with an inwardly open annular groove constituting a fluidinlet compartment and another inwardly open annular groove constituting a fluid-outlet compartment, said annular grooves being axially spaced apart and both open- 40 ing in the direction of said plunger, said plunger being formed with an outwardly open circumferential channel interconnecting said compartments in a neutral position of said plunger, said channel having a pair of axially spaced flanks defining a channel mouth and having a base, said flanks at least partly overhanging said base whereby fluid flowing from said inlet compartment to said outlet compartment applies a component of force to said plunger in aiding relationship to said restoring force and tending to return said plunger to said neutral position upon its displacement therefrom, said flanks being at least in part formed by blind bores provided in said member and inclined to the axis of said plunger from said channel while extending outwardly from said channel and opening into the channel below the mouth thereof, said bores 5 converging toward said axis and lying generally on a frustoconical surface coaxial with said plunger.

References Cited UNITED STATES PATENTS M. CARY NELSON, Primary Examiner M. O. STURM, Assistant Examiner US. Cl. X.R.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3.525.500 Dated 25 August 1970 InventOr( Alfred BENDER It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Col. 1, line 7, should read Claims priority, application Germany, Feb. 14, 1967 Claim 1, line 16 (col. 4, line 8), change "forcing" to forming SIGNED Mu EAIE nets-19D (SEAL) Attest:

Edward M. Fletcher, Jr.

WILLIAM 1!. sum, JR. LA 0mm Oomissionar of Patents J 

